title: A promoter relay mechanism for sequential gene activation.
abstract: The effect of DNA supercoiling on gene expression is dependent not only on specific genes but also on the sequence context of the genes. This position-dependent supercoiling effect on gene activation is best illustrated in the study of the suppression of the leu-500 mutation of the leuABCD operon in a Salmonella typhimurium topA mutant. In this communication, we report a novel promoter relay mechanism whereby several genes are sequentially expressed in a position-dependent manner: the ilvIH promoter (pilvIH) activates a cryptic leuO promoter (pleuO) located between the two divergently arrayed ilvIH and leu-500 promoters. Both the cis-acting pleuO activity and the trans-acting LeuO protein are necessary for subsequent activation of the leu-500 promoter (pleu-500). Furthermore, pleuO can be functionally replaced with the inducible tac promoter (ptac) for leu-500 activation, suggesting that transcription-driven DNA supercoiling underlies the relay mechanism. This is the first example of several related genes communicating via a promoter relay mechanism for their coordinated expression.
authors.affiliation: Department of Pharmacology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: M
authors.initials: M
authors.lastname: Fang
authors.forename: H Y
authors.initials: HY
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012486:Salmonella typhimurium / Q000235:genetics*; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; C077573:PilV protein, Bacteria